This invention is in the general field of wiring systems applied to vehicles and particularly to motor vehicles such as automobiles. It specifically addresses the use of a common wire bus or data bus for a plurality of sensors and actuators in a motor vehicle and particularly for safety systems including crash, occupant and other sensors, airbag modules and associated electronics.
This invention also relates to the field of inflator devices for inflating airbag occupant restraints mainly for the protection of occupants of automobiles and trucks although it also is applicable to the protection of occupants of other vehicles and for inflating other inflatable objects. In particular, by means of the present invention, a more efficient utilization of the energy in a propellant is attained resulting in the need for a lower amount of propellant than in currently existing inflators, and thus a smaller inflator, to inflate a given size inflatable object. This is accomplished in part through a more efficient aspirating nozzle design and an improved geometry of a gas generator that houses the propellant.
The present invention additionally relates to an airbag system for use in vehicles having multiple airbags where the possibility exists that more than two airbags will be deployed in a given accident resulting in excessive pressure within the passenger compartment of the vehicle, and which optionally utilize the inflator devices described above.
The present invention also relates to airbag systems including inflator devices using wider classes of propellants that produce gases that are toxic to humans if breathed for an extended time period.
The present invention additionally relates to an efficient airbag module whereby much of the electronics which are part of the airbag system are associated with the module including occupant sensing components, the backup power supply and diagnostic circuitry.
It is not uncommon for an automotive vehicle today to have many motors, other actuators, lights etc., controlled by one hundred or more switches and fifty or more relays and connected together by almost five hundred meters of wire, and close to one thousand pin connections grouped in various numbers into connectors. It is not surprising therefore that the electrical system in a vehicle is by far the most unreliable system of the vehicle and the probable cause of most warranty repairs.
Unfortunately, the automobile industry is taking a piecemeal approach to solving this problem when a revolutionary approach is called for. Indeed, the current trend in the automotive industry is to group several devices of the vehicle""s electrical system together which are located geometrically or physically in the same area of the vehicle and connect them to a zone module which is then connected by communication and power buses to the remainder of the vehicle""s electrical system. The resulting hybrid systems still contain substantially the same number and assortment of connectors with only about a 20% reduction in the amount of wire in the vehicle.
Most airbag modules in use today are large, heavy, expensive, and inefficient. As a result, airbags are now primarily only used for protecting the passenger and driver in a frontal impact, although at least three automobile manufacturers currently offer a small airbag providing limited protection in side impacts and some are now offering head protection airbags. The main advantage of airbags over other energy absorbing structures is that they utilize the space between the occupant and vehicle interior surfaces to absorb the kinetic energy of the occupant during a crash, cushioning the impending impact of the occupant with the vehicle interior surfaces. Airbags have been so successful in frontal impacts that it is only a matter of time before they are effectively used for side impact protection in all vehicles, protection for rear seat occupants and in place of current knee bolsters. Substantial improvements, however, must be made in airbags before they assume many of these additional tasks A good place to start describing the problems with current airbags is with a calculation of the amount of energy used in a typical airbag inflator and how much energy is required to inflate an airbag. By one analysis, the chemical propellant in a typical driver""s side inflator contains approximately 50,000 foot pounds (68,000 joules) of energy. A calculation made to determine the energy required to inflate a driver""s side airbag yields an estimate of about 500 foot pounds (680 joules). A comparison of these numbers shows that approximately 99% of the energy in a chemical propellant is lost, that is, generated but not needed for inflation of the airbag. One reason for this is that there is a mismatch between the output of a burning propellant and the inflation requirements of an airbag. In engineering this is known as an impedance mismatch. Stated simply, propellants naturally produce gases having high temperatures and high pressures and low gas flow rates. Airbags, on the other hand, need gases with low temperatures and low pressures and high gas flow rates.
In view of this impedance mismatch, inflators are, in theory at least, many times larger then they would have to be if the energy of the propellant contained within the inflator were efficiently utilized. Some attempts to partially solve this problem have resulted in a so-called xe2x80x9chybridxe2x80x9d inflator where a stored pressurized gas is heated by a propellant to inflate the airbag. Such systems are considerably more energy efficient, however, they also require a container of high pressure gas and means for monitoring the pressure in that container. Other systems have attempted to use aspiration techniques, but because of the geometry constraints of current car inflator designs and mounting locations, and for other reasons, currently used aspiration systems are only able to draw significantly less than 30% of the gas needed to inflate an airbag from the passenger compartment. Theoretical studies have shown that as much as 90% or more of the gas could be obtained in this manner.
Furthermore, since inflators are large and inefficient, severe restrictions have been placed on the type of propellants that can be used since the combustion products of the propellant must be breathable by automobile occupants. It is of little value to save an occupant from death in an automobile accident only to suffocate him from an excessive amount of carbon dioxide in the air within the passenger compartment after the accident. If inflators operated more efficiently, then alternate, more efficient but slightly toxic propellants could be used. Also, most current inflators are made from propellants, namely sodium azide, which are not totally consumed. Only about 40% of the mass of sodium azide propellants currently being used, for example, enters the airbag as gas. This residual mass is very hot and requires the inflator to be mounted away from combustible materials further adding to the mass and size of the airbag system and restricts the materials that can be used for the inflator.
It is a persistent problem in the art that many people are being seriously injured or even killed today by the airbag itself This generally happens when an occupant is out-of-position and against an airbag module when the airbag deploys. In order to open the module cover, sometimes called the deployment door, substantial pressure must first build up in the airbag before enough force is generated to burst open the cover. This pressure is even greater if the occupant is in a position that prevents the door from opening. As a result, work is underway to substantially reduce the amount of energy required to open the deployment doors and devices have been developed which pop off the deployment door or else cut the deployment door material using pyrotechnics, for example.
One reason that this is such a significant problem is that the airbag module itself is quite large and, in particular, the airbags are made out of thick, heavy material and packaged in a poor, folded geometry. The airbag, for example, which protects the passenger is housed in a module which is typically about one third as long as the deployed airbag. All of this heavy airbag material must be rolled and folded inside this comparatively small module, thus requiring substantial energy to unfold during deployment. This situation could be substantially improved if the airbag module were to have an alternate geometry and if the airbag material were substantially lighter and thinner and, therefore, less massive and folded mainly parallel to the inflator. Even the time to deploy the airbag is substantially affected by the mass of the airbag material and the need to unfold an airbag with a complicated folding pattern. Parallel folding, as used herein, means that the airbag material is folded with the fold lines substantially parallel to the axis of the inflator without being folded over lengthwise as is now done with conventional airbag folding patterns.
Devices are now being offered on vehicles that will monitor the position of the occupant and prevent the airbag from deploying if the occupant is dangerously close to the module where he or she can be seriously injured by the deployment. Some systems will also prevent deployment if the seat in connection with which the airbag operates is unoccupied. An alternate approach is to move the deployment doors to a location away from normal occupant positions. One such location is the ceiling of the vehicle. One problem with ceiling mounted airbags is that the distance required for the airbag to travel, in some cases, is longer and therefore a larger airbag is needed with greater deployment time. With the use of light airbag materials, such as thin plastic film, as disclosed in the above-referenced U.S. Pat. Nos. 5,505,485 and 5,653,464, and the use of more efficient inflators, both of these problems can be solved especially for the front and rear seat passengers. The driver poses a different problem since it would be difficult to position a ceiling mounted airbag module where the airbag would always be projected properly between the occupant and the steering wheel. On the other hand, the driver can usually ride down on the steering wheel if he or she is initially positioned close to it.
This problem for the driver""s airbag system is not the concept of mounting the airbag on the ceiling, but the design of the steering wheel and steering column. These designs come from the time when the only way of steering an automobile was through mechanical linkages. The majority of vehicles manufactured today have power assisted steering systems and, in fact, most drivers would have difficulty steering a car today if the power steering failed. If servo power steering were used, the need for a mechanical linkage between a steering wheel, or other such device, and the power steering system would no longer be necessary. Servo power steering for the purposes here will mean those cases where the linkage between the manually operated steering device, which regardless of what that device is, will herein be called a steering wheel, is done with a servo system either electrically or hydraulically and the system does not have an operative mechanical connection between the steering wheel and the steering mechanism which moves the wheels.
The problem of educating the general population, which has become secure in the feeling of a steering wheel and steering column, might be insurmountable if it were not for the substantial safety advantage resulting from substituting servo power steering for conventional steering systems and using a non-steering wheel mounted airbag module for the driver.
The steering wheel and steering column are among the most dangerous parts of the vehicle to the occupant. Small people, for example, who are wearing seatbelts can still be seriously injured or killed in accidents as their faces slam into the steering wheel hubs. The problem of properly positioning an airbag, when the comfort and convenience features of telescoping and tilting steering columns are considered, results in substantial safety compromises. Deployment induced injuries which result when a small person is close to the steering wheel when the airbag deploys have already caused several deaths and numerous serious injuries. Future vehicles, therefore, for safety reasons should be constructed without the massive steering wheel and steering column and substitute therefor a servo steering assembly. With this modification, a ceiling mounted airbag module, such as discussed herein, becomes feasible for the driver as well as the other seating positions in the vehicle.
The front seat of the vehicle today has an airbag for the passenger and another for the driver. In some accidents, an occupant, and particularly a center-seated occupant, can pass between the two airbags and not receive the full protection from either one. If a ceiling mounted airbag system were used, a single airbag could be deployed to cover the entire front seat greatly simplifying the airbag system design.
One method of partially solving many of these problems is to use an efficient aspirated airbag system. There have been numerous patents granted on designs for airbag systems using aspirated inflators. In these patents as well as in the discussion herein the term xe2x80x9cpumping ratioxe2x80x9d is used. The pumping ratio as used in the art is defined as the ratio of the mass of gas aspirated from the environment, either from inside or outside of the vehicle, to the mass of gas generated by burning the propellant. A brief description of several pertinent aspiration patents, all of which are included herein by reference, follows:
U.S. Pat. No. 2,052,869 to Coanda illustrates the manner in which a fluid jet is caused to change direction, although no mention is made of its use in airbags. This principle, the xe2x80x9cCoanda effectxe2x80x9d, is used in some implementations of the instant invention as well as in U.S. Pat. No. 3,909,037 to Stewart discussed below. It""s primary contribution is that when used in inflator designs, it permits a reduction in the length of the nozzle required to efficiently aspirate air into the airbag. No disclosure is made of a pumping ratio in this system and in fact it is not an object of Coanda to aspirate fluid.
U.S. Pat. No. 3,204,862 to Hadeler also predates the invention of vehicular airbags but is nonetheless a good example of the use of aspiration to inflate an inflatable structure. In this device, an inflating gas is injected into an annular converging-diverging nozzle and some space efficiency is obtained by locating the nozzle so that the flow is parallel to the wall of the inflatable structure. No mention is made of a pumping ratio of this device and furthermore, this device is circular.
U.S. Pat. No. 3,632,133 to Hass provides a good example of a nozzle in a circular module with a high pumping ratio in an early construction of an airbag. Although analysis indicates that pumping ratios of 4:1 or 5:1 would be difficult to achieve with this design as illustrated, nevertheless, this reference illustrates the size and rough shape of an aspirating system which is required to obtain high pumping ratios using the prior art designs.
U.S. Pat. No. 3,909,037 to Stewart provides a good example of the application of the Coanda effect to airbag aspirating inflators. Stewart, nevertheless, still discards most of the energy in the propellant which is absorbed as heat in the inflator mechanism. Most propellants considered for airbag applications burn at pressures in excess of about 1000 psig. Stewart discloses that the maximum efficiency corresponding to a 5:1 pumping ratio occurs at inflator gas pressures of about 5 to about 45 psig. In order to reduce the pressure, Stewart utilizes a complicated filtering system similar to that used in conventional inflators. Stewart requires the use of valves to close off the aspiration ports when the system is not aspirating. Through the use of the Coanda effect, Stewart alludes to a substantial reduction in the size of the aspiration system, compared to Hass for example. Also, Stewart shows only a simple converging nozzle through which the burning propellant is passed.
U.S. Pat. No. 4,833,996 to Hayashi et al. describes a gas generating apparatus for inflating an airbag which is circular and allegedly provides an instantaneous pumping ratio of up to 7:1 although analysis shows that this is unlikely in the illustrated geometry. The average pumping ratio is specified to be up to 4:1. This invention is designed for the driver side of the vehicle where unrestricted access to the aspirating port might be difficult to achieve when mounted on a steering wheel. The propellant of choice in Hayashi et al. is sodium azide which requires extensive filtering to remove particulates. No attempt has been made in this design to optimize the nozzle geometry to make use of a converging-diverging nozzle design, for example. Also, the inflator has a roughly conventional driver side shape. It is also interesting to note that no mention is made of valves to close off or restrict flow through the aspiration port during deflation. Since most aspiration designs having even substantially smaller pumping ratios provide for such valves, the elimination of these valves would be a significant advance in the art. Analysis shows, however, that the opening needed for the claimed aspiration ratios would in general be far too large for it also to be used for exhausting the airbag during a crash. Since this is not discussed, it should be assumed that valves are required but not illustrated in the figures.
U.S. Pat. No. 4,877,264 to Cuevas describes an aspirating/venting airbag module assembly which includes a circular gas generator and contemplates the use of conventional sodium azide propellants or equivalent. The aspiration or pumping ratio of this inflator is approximately 0.2:1, substantially below that of Hayashi et al., but more in line with aspiration systems in common use today. This design also does not require use of aspiration valves which is more reasonable for this case, but still unlikely, since the aspiration port area is much smaller. Again, no attempt has been made to optimize the nozzle design as is evident by the short nozzle length and the low pumping ratio.
U.S. Pat. No. 4,909,549 to Poole et al. describes a process for inflating an airbag with an aspiration system but does not discuss the aspiration design or mechanism and merely asserts that a ratio as high as 4:1 is possible but assumes that 2.5:1 is available. This patent is significant in that it discloses the idea that if such high pumping ratios are obtainable (i.e., 2.5:1 compared with 0.2:1 for inflators in use), then certain propellants, which would otherwise be unacceptable due to their production of toxic chemicals, can be used. For example, the patent discloses the use of tetrazol compounds. It is interesting to note that there as yet is no commercialization of the Poole et al. invention which raises the question as to whether such high aspiration ratios are in fact achievable with any of the prior art designs. Analysis has shown that this is the case, that is, that such large aspiration ratios are not achievable with the prior art designs.
U.S. Pat. No. 4,928,991 to Thorn describes an aspirating inflator assembly including aspiration valves which are generally needed in all high pumping ratio aspiration systems. Sodium azide is the propellant used. Pumping ratios of 1:1 to 1.5:1 are mentioned in this patent which by analysis is possible. It is noteworthy that the preamble of this patent discloses that the state of the art of aspirating inflators yields pumping ratios of 0.1:1 to 0.5:1, far below those specified in several of the above referenced earlier patents. Once again, little attempt has been made to optimize the nozzle design.
U.S. Pat. No. 5,004,586 to Hayashi et al. describes a sodium azide driver side inflator in which the aspirating air flows through a series of annular slots on the circumference of the circular inflator in contrast to the earlier Hayashi et al. patent where the flow was on the axis. Similar pumping ratios of about 4:1 are claimed however, which by analysis is unlikely. Once again, aspiration valves are not shown and the reason that they can be neglected is not discussed. An inefficient nozzle design is again illustrated. The lack of commercial success of these two Hayashi patents is probably due to the fact that such high pumping ratios as claimed are not in fact achievable in the geometries illustrated.
U.S. Pat. No. 5,060,973 to Giovanetti describes the first liquid propellant airbag gas generator wherein the propellant bums clean and does not require filters to trap solid particles. Thus, it is one preferred propellant for use in the instant invention. This system however produces a gas which is too hot for use directly to inflate an airbag. The gas also contains substantial quantities of steam as well as carbon dioxide. The steam can cause bums to occupants and carbon dioxide in significant quantities is toxic. The gas generator is also circular. Aspirating systems are therefore required when using the liquid propellant disclosed in this patent, or alternately, the gas generated must be exhausted outside of the vehicle.
U.S. Pat. No. 5,129,674 to Levosinski describes a converging-diverging nozzle design which provides for more efficient aspiration than some of the above discussed patents. Nevertheless, the airbag system disclosed is quite large and limited in length such that the flow passageways are quite large which requires a long nozzle design for efficient operation. Since there is insufficient space for a long nozzle, it can be estimated that this system has a pumping ratio less than 1:1 and probably less than 0.2:1. Once again a sodium azide based propellant is used.
U.S. Pat. No. 5,207,450 to Pack, Jr. et al. describes an aspirated air cushion restraint system in which no attempt was made to optimize the nozzle design for this sodium azide driver side airbag. Also, aspiration valves are used although it is suggested that the exhaust from the airbag can be made through the aspirating holes thereby eliminating the need for the flapper valves. No analysis, however, is provided to prove that the area of the aspiration holes is comparable to the area of the exhaust holes normally provided in the airbag. Although no mention is made of the pumping ratio of this design, the device as illustrated appears to be approximately the same size as a conventional driver side inflator. This, coupled with an analysis of the geometry, indicates a pumping ratio of less than 1:1 and probably less than 0.2:1. The statement that the aspiration valves are not needed also indicates that the aspiration ratio must be small. Large inlet ports which are needed for large aspiration ratios are generally much larger than the typical airbag exhaust ports.
U.S. Pat. No. 5,286,054 to Cuevas describes an aspirating/venting motor vehicle passenger airbag module in which the principal of operation is similar to the ""264 patent discussed above. Once again the aspiration pumping ratio of this device is 0.15:1 to 0.2:1 which is in line with conventional aspirated inflators. It is interesting to note that this pioneer in the field does not avail himself of designs purporting to yield higher pumping ratios. Again the nozzle design has not been optimized.
Other U.S. patents which are relevant to the instant invention but which will not be discussed in detail are: U.S. Pat. No. 3,158,314 to Young et al., U.S. Pat. No. 3,370,784 to Day, U.S. Pat. No. 5,085,465 to Hieahim, U.S. Pat. No. 5,100,172 to Van Voorhies et al., U.S. Pat. No. 5,193,847 to Nakayama, U.S. Pat. No. 5,332,259 to Conlee et al. and U.S. Pat. No. 5,423,571 to Hawthorn.
None of the prior art inflators contain the advantages of the combination of (i) a linear inflator having a small cross section thereby permitting an efficient nozzle design wherein the length of the nozzle is much greater than the aspiration port opening, (ii) a non sodium azide propellant which may produce toxic gas if not diluted with substantial quantities of ambient air, and (iii) an inflator where minimal or no filtering or heat absorption is required.
It is interesting to note that in spite of the large aspiration pumping ratios mentioned and even claimed in the prior art references mentioned above, and to the very significant advantages which would result if such ratios could be achieved, none has been successfully adapted to an automobile airbag system. One reason is that pumping ratios which are achievable in a steady state laboratory environment are more difficult to achieve in the transient conditions of an actual airbag deployment.
None of these prior art designs have resulted in a thin linear module which permits the space necessary for an efficient nozzle design as disclosed herein. In spite of the many advantages claimed in the prior art patents, none have resulted in a module which can be mounted within the vehicle headliner trim, for example, or can be made to conform to a curved surface. In fact, the rigid shape of conventional airbag modules has forced the vehicle interior designers to compromise their designs since the surface of such modules must be a substantially flat plane.
With respect to airbag systems including a plurality of inflatable airbags or unconventionally large airbags and inflators therefor, automobile manufacturers are now installing more than two airbags into a vehicle. The placement of both side and rear seat airbags have in fact taken place by at least one manufacturer each; Nissan for rear airbags and Volvo, General Motors and Ford for side airbags. However, Nissan has stated that it cannot provide more than a total of two airbags in the vehicle and that it will not offer a front passenger side airbag for those vehicles that have a rear seat airbag. With respect to the Volvo, General Motors and Ford airbags, these side airbags will not deploy when the frontal airbags do because if more than two airbags would be deployed in a vehicle at the same time, the pressure generated by the deploying airbags within the passenger compartment of the vehicle creates large forces on the doors. These forces may be sufficient to force the doors open and consequently, if the doors of the vehicle are forced open during a crash, vehicle occupants might be ejected, greatly increasing the likelihood of serious injury. In addition, the pressure generated within the passenger compartment creates excessive noise which can injure human beings.
In addition to airbags for side impacts and rear seats, it is likely that airbags will be used as knee bolsters since automobile manufacturers are having serious problems protecting knees from injury in crashes while providing the comfort space desired by their customers.
As soon as three or more airbags are deployed in an accident, provisions should be made to open a hole in the vehicle to permit the pressure generated by the deploying airbags to escape. What has not heretofore been appreciated, however, is that once there is a significant opening from the vehicle to the outside, the requirements for the composition of the inflator gases used to inflate the airbags change and inflators which generate a significant amount of toxic gas become feasible, as will be discussed below.
The primary gas generating propellant used in airbag systems today is sodium azide. This is partially due to the fact that when sodium azide burns, in the presence of an oxidizer, it produces large amounts of Nitrogen gas. It also produces sodium oxide which must be retained in the inflator since sodium oxide, when mixed with moisture, becomes lye and is very toxic to humans. Thus, current inflators emit only nitrogen gas into the passenger compartment which occupants can breath for a long period of time in a closed passenger compartment without danger. The sodium azide inflators also are large to accommodate the fact that about 60% of the gas generating material remains in the inflator with only about 40% emerging as gas.
Other propellants, including nitrocellulose, nitroguanidine, and other double base and triple base formulations, as well as a large number of liquid propellants, exist which could be used to inflate airbags, however they usually produce various quantities of gases containing compounds of nitrogen and oxygen plus significant amounts of carbon dioxide. In many cases, the gases produced by these other propellants are only toxic to humans if breathed over an extended period of time. If the toxic gas were removed from the vehicle within a few minutes after the accident then many of these propellants would be usable to inflate airbags.
Much of the energy released when sodium azide bums in the inflator is removed from the gas by the cooling and filtering screens. In some designs, the sodium oxide must be trapped by the filters which requires that the gas be cooled to the point where sodium oxide condenses. In all designs, the gas is cooled so that the temperature of the gas in the airbag will not cause bums to the occupants. It is believed that in all current designs, a substantial amount of the energy in a propellant is lost through this cooling process which in turn necessitates that the inflator contain more propellant.
Airbag systems have primarily been installed within the instrument panel or steering wheel of automobiles. As a result, although numerous attempts have been made to create aspirated inflator systems, they have only been used on the passenger side and their efficiency has been low. In aspirated inflator systems, part of the gas to inflate the airbag is drawn in from the passenger compartment. However, in a typical passenger side airbag system in use today where aspiration is employed, substantially less than about 30% of the gas which inflates the airbag comes from the passenger compartment and some researchers state that it is even below about 5%. In view of the large size of conventional sodium azide inflators and woven airbags, there is limited room for the airbag system and it is difficult to design aspirating systems which will fit within the remaining available space. One reason is the resistance of the air flow through the instrument panel into the aspirator. Another reason for the low efficiency of aspirated inflator systems is that the aspirated systems used today have inefficient nozzle designs. Theoretical studies of aspiration systems, such as described herein, show that the percentage of gas drawn in from the passenger compartment could be raised to as high as about 75% or even 90%.
One airbag aspiration method is described in U.S. Pat. No. 4,909,549 to Poole et al. Poole et al. describes a method for inflating an airbag in which a substantially non-toxic primary gas mixture is diluted with outside air by passing the primary gas mixture through a venturi to aspirate the air. Poole et al. does not suggest that the outside air should come from the passenger compartment and therefore does not provide a solution to the problem of excessive pressure being generated in the passenger compartment upon deployment of multiple airbags, as discussed above.
If alternate, more efficient propellants are used and if the gas produced thereby is exhausted at a much higher temperature, more of the energy would be available to heat the gas which is flowing from the passenger compartment to the airbag thus further increasing the efficiency of the system and reducing the amount of propellant required. Since cooling screens are not necessary and since the efficiency of the propellant is high, the inflator can be made very small providing the extra space needed to design efficient aspirating nozzles.
Since many alternate propellants produce toxic gases, their use becomes practical (i) if the quantity used is substantially reduced, (ii) if means are provided to prevent the gas from entering the occupant compartment, or (iii) if means exist within the vehicle to exhaust the toxic gas from the vehicle shortly after the airbag is deployed.
Finally, today the airbag electronics are housed separate and apart from the airbag module and the energy needed to initiate the inflator is transmitted to the airbag module after the crash sensor has determined that the airbag deployment is required. This has resulted in many failures of the airbag system due to shorted wires and other related causes. This and other problems could be solved if the crash sensor electronics send a coded signal to the airbag module and the electronics associated with the module decoded the signal to initiate the inflator. The diagnostics circuitry can then also be part of or associated with the module along with the backup power supply which now also becomes the primary power supply for the module.
These and other problems of current airbag systems are solved by the invention disclosed herein and described in detail below.
Preferred embodiments of the invention are described below and unless specifically noted, it is the applicant""s intention that the words and phrases in the specification and claims be given the ordinary and accustomed meaning to those of ordinary skill in the applicable art(s). If applicant intends any other meaning, he will specifically state they are applying a special meaning to a word or phrase.
Likewise, applicant""s use of the word xe2x80x9cfunctionxe2x80x9d here is not intended to indicate that the applicant seeks to invoke the special provisions of 35 U.S.C. xc2xa7112, sixth paragraph, to define their invention. To the contrary, if applicant wishes to invoke the provisions of 35 U.S.C. xc2xa7112, sixth paragraph, to define their invention, he will specifically set forth in the claims the phrases xe2x80x9cmeans forxe2x80x9d or xe2x80x9cstep forxe2x80x9d and a function, without also reciting in that phrase any structure, material or act in support of the function. Moreover, even if applicant invokes the provisions of 35 U.S.C. xc2xa7112, sixth paragraph, to define his invention, it is the applicant""s intention that his inventions not be limited to the specific structure, material or acts that are described in the preferred embodiments herein. Rather, if applicant claims his inventions by specifically invoking the provisions of 35 U.S.C. xc2xa7112, sixth paragraph, it is nonetheless his intention to cover and include any and all structure, materials or acts that perform the claimed function, along with any and all known or later developed equivalent structures, materials or acts for performing the claimed function.
Accordingly, it is an object of the present invention to provide a new and improved electrical wiring system for coupling sensors and actuators in a motor vehicle in order to reduce the amount of wire in the motor vehicle and improve system reliability.
It is a particular object of this invention to provide a vehicle safety wiring system including a network comprising various safety devices such as crash sensors and airbag inflator igniters.
It is a further object of the present invention to provide a new and improved airbag module in which the disadvantages and problems in the prior art airbag module designs are substantially eliminated.
It is another object of the present invention to provide a new and improved airbag module in which the propellant is utilized more efficiently than in prior art constructions, i.e., more of the energy generated by the burning propellant is used to inflate the airbag with less waste of generated energy.
It is yet another object of the present invention to provide a new and improved airbag module in which the propellant is utilized more efficiently than in prior art constructions so that a smaller amount of propellant can be used thereby enabling a wider variety of propellants, which may generate toxic gases, to be used since only small quantities of such toxic gases will be generated.
It is still another object of the present invention to provide a new and improved airbag module which is designed so that if an occupant is out-of-position and leaning against the module, the module will still enable deployment of the airbag to protect the occupant.
It is another object of the present invention to provide a new and improved airbag module in which a more efficient aspirating system is used, i.e., one having a larger pumping ratio.
It is yet another object of the present invention to associate much of the airbag electronics with the airbag module so as to improve the reliability of the system.
It is a further object of the present invention to permit the deployment of both the frontal and side airbags during a primarily frontal crash to reduce the probability of injury to the occupants through impacts with the passenger compartment.
Other principle objects and advantages of this invention are:
1. To provide a long, thin airbag module which can be conveniently mounted on the ceiling or almost any other surface of the vehicle for the protection of vehicle occupants in frontal collisions.
2. To provide a highly efficient airbag module which uses the minimum amount of propellant.
3. To provide a rapidly deploying airbag module causing minimal injury to out-of-position occupants.
4. To provide an airbag module where a single module can be used to protect both a front and a rear passenger of the vehicle in side impacts.
5. To provide a cover system for the module which is easily released thereby reducing the risk of deployment induced injuries to the vehicle occupants.
6. To provide an airbag module which can be conveniently mounted on the instrument panel, or knee bolster support structure, to provide knee and leg protection for the vehicle occupant as well as for an occupant, such as a child, lying on the seat.
7. To provide a driver protection airbag system for use with vehicles having servo power steering and thereby promote the elimination of the massive steering column and steering wheel.
8. To provide an airbag module which is displaced from its mounting surface during the initial stage of airbag deployment to thereby opening aspirating channels.
9. To provide a highly efficient aspirated airbag module.
10. To provide a long thin airbag module where the module is approximately the same length as the inflated airbag thereby simplifying the folding, and unfolding during deployment, of the airbag and permit more rapid airbag deployment.
11. To provide an airbag module which is easily replaced when the vehicle is repaired after an accident.
12. To provide a ceiling mounted airbag module for protection of rear seated occupants.
13. To provide an aspirated airbag system where the aspiration inlet ports are also used as the venting ports for the airbag, including an automatic adjustment system to reduce the vent area, thereby simplifying the airbag design by removing the requirement for vents within the airbag material.
14. To provide an inflator design wherein the propellant is a single solid material attached to the inside of the inflator housing thereby simplifying the inflator design and providing a definable burning surface.
15. To provide a method of ignition of a propellant through a coating placed on the surface of a propellant containing an igniter material such as BKNO3.
16. To provide a thin airbag module which can be mounted substantially on a surface of the passenger compartment such as the ceiling, instrument panel, or seat back without penetrating deeply within the surface.
17. To provide for a thin airbag module which can be made to conform to a curved surface.
18. To provide an inflator design wherein the propellant is a liquid substantially filling the inside of the inflator housing thereby simplifying the inflator design and providing a definable burning surface.
19. To provide new and improved methods and apparatus which permit the use of propellants in inflators for airbag system which otherwise would not be usable due to their toxicity.
20. To provide an airbag system where multiple airbags are deployed in a vehicle and where the gas used to inflate the airbags is toxic to humans but is removed from the passenger compartment before it causes injury to the occupants, thereby permitting the use of heretofore unusable toxic propellants.
21. To provide a system to relieve the excess pressure generated by the, deployment of multiple airbags thereby preventing the doors from being inadvertently opened by this excess pressure.
22. In particular, to provide a method of breaking a window in the vehicle to relieve the excess pressure and create a path for toxic gases and excess pressure to escape.
23. To provide a system which only deploys those airbags in the vehicle which are likely to help prevent occupants from being injured, thereby minimizing the total number of airbags deployed during a crash.
24. To provide an airbag deployment delay system within one or more of the airbag modules in order to reduce the peak pressure and noise within the vehicle.
25. To permit the use of large knee protection airbags which helps reduce injuries to an occupant who is lying on a seat during an accident.
26. To provide protection for an occupant from the impact with various vehicle roof support pillars in the event of a frontal angular impact, or other impact, by providing side protection airbags which are deployed along with the frontal impact protection airbags through a method of relieving the excess pressure caused by the deployment of multiple airbags.
27. To provide a system which permits more than two airbags to be deployed during a single crash event.
Sometimes, when a component fails, a catastrophic accident results. In the Firestone tire case, for example, over 100 people were killed when a tire of a Ford Explorer blew out which caused the Ford Explorer to rollover. Similarly, other component failures can lead to loss of control of the vehicle and a subsequent accident. It is thus very important to accurately forecast that such an event will take place but furthermore, for those cases where the event takes place suddenly without warning, it is also important to diagnose the state of the entire vehicle, which in some cases can lead to automatic corrective action to prevent unstable vehicle motion or rollovers resulting in an accident. Finally, an accurate diagnostic system for the entire vehicle can determine much more accurately the severity of an automobile crash once it has begun by knowing where the accident is taking place on the vehicle (e.g., the part of or location on the vehicle which is being impacted by an object) and what is colliding with the vehicle based on a knowledge of the force deflection characteristics of the vehicle at that location. Therefore, in addition to a component diagnostic, the teachings of this invention also provide a diagnostic system for the entire vehicle prior to and during accidents. In particular, this invention is concerned with the simultaneous monitoring of multiple sensors on the vehicle so that the best possible determination of the state of the vehicle can be determined. Current crash sensors operate independently or at most one sensor may influence the threshold at which another sensor triggers a deployable restraint. In the teachings of this invention, two or more sensors, frequently accelerometers and/or gyroscopes, can be monitored simultaneously and the combination of the outputs of these multiple sensors are combined continuously in making the crash severity analysis. Also, according to the teachings of this invention, all such devices can communicate on a single safety bus that connects the various safety related electronics, sensors and actuators such as airbag modules, seatbelt retractors, and vehicle control systems.
In order to achieve one or more of the objects set forth above, an airbag deployment system for a vehicle in accordance with the invention comprises a module housing, an airbag associated with the housing, an inflator or inflator assembly arranged in the housing for inflating the airbag, and inflation determining means for generating a signal indicative of whether deployment of the airbag is desired. The inflation determining means preferably comprise one or more crash sensors, at least one of which is arranged separate and at a location apart from the housing. An electronic controller is arranged in or adjacent the housing and coupled to the inflation determining means. The controller controls inflation of the airbag by the inflator assembly in response to the signal generated by the inflation determining means. An electrical bus electrically couples the controller and the inflation determining means whereby the signal from the inflation determining means is sent over the bus to the controller to enable inflation of the airbag. The bus may consists of a single pair of wires over which power and information is conveyed. A sensor and diagnostic module is also coupled to the bus for monitoring the controller. The inflation determining means, e.g., crash sensor, is designed to preferably generate a coded signal when deployment of the airbag is desired which coded signal is conveyed over the bus to the controller to enable the controller to control inflation of the airbag by the inflator assembly based thereon. The controller will preferably include a power supply for enabling initiation of the inflator assembly. An occupant position sensor, e.g., an ultrasonic transmitter/receiver pair, may be arranged to detect the position of the occupant to be protected by the airbag in which case, the controller would control inflation of the airbag by the inflator assembly in consideration of the detected position of the occupant. The occupant position sensor may be arranged in the same housing as the inflator assembly, airbag and controller.
An embodiment of an occupant protection system in accordance with the invention comprises a plurality of occupant protection devices, each comprising a housing and a component deployable to provide protection for the occupant (such as an airbag), and deployment determining means for generating a signal indicating for which of the deployable components deployment is desired, e.g., one or more crash sensors which may be located around the vehicle and preferably separate and at locations apart from the same housings as the deployable components. An electronic controller is arranged in, proximate or adjacent each housing and coupled to the deployment determining means. Each controller controls deployment of the deployable component of the respective occupant protection device in response to the signal generated by the deployment determining means. An electrical bus electrically couples the controllers and deployment determining means so that the signal from the deployment determining means is sent over the bus to the controllers to enable deployment of the deployable components. A sensor and diagnostic module may be coupled to the bus for monitoring the controllers. The deployment determining means preferably generate a coded signal when deployment of one or more of the deployable components is desired so that since each controller initiates deployment of the respective deployable component only if the coded signal contains a specific initiation code associated with the controller. An occupant position sensor could also be provided to detect the position of the occupant to be protected by the deployable components so that the controller of any of the deployable components would control deployment thereof in consideration of the detected position of the occupant.
One embodiment of an occupant protection system, for a vehicle in accordance with the invention comprises an occupant protection device for protecting an occupant in the event of a crash involving the vehicle, initiation means for initiating deployment of the occupant protection device, power means for storing sufficient energy to enable the initiation means to initiate deployment of the occupant protection device, an electronic controller connected to the power means for monitoring voltage of the power means and controlling the initiation means, a diagnostic module arranged to receive a signal from the controller as to whether the voltage of the power means is sufficient to enable the initiation means to initiate deployment of the occupant protection device, and an electrical bus electrically coupling the controller and the diagnostic module. The controller is arranged to generate a fault code in the event of a failure of the power means or the initiation means, which fault code is sent to the diagnostic module over the bus. One or more crash sensors or other deployment determining means are preferably coupled to the bus for generating a (coded) signal indicative of whether deployment of the occupant protection device is desired, the signal being sent from the determining means over the bus to the controller. The controller may be arranged in the housing or adjacent the housing.
Another embodiment of an occupant protection system in accordance with the invention comprises a deployable occupant protection device, deployment determining means for generating a coded signal indicative of whether deployment of the occupant protection device is desired, and an electrical bus electrically coupling the occupant protection device and the deployment determining means. The coded signal from the deployment determining means is sent over the bus to the occupant protection device to enable deployment of the occupant protection device. The deployment determining means may comprise one or more crash sensors arranged separate and at locations apart from the occupant protection device. A controller may be coupled to the deployment determining means, the occupant protection device and the bus, and controls deployment of the occupant protection device in response to the coded signal generated by the deployment determining means. The coded signal from the deployment determining means is sent over the bus to the controller to enable deployment of the occupant protection device.
A method for controlling deployment of an occupant protection system for protecting an occupant in a vehicle comprises the steps of arranging a deployable occupant protection device in the vehicle, generating a coded signal indicative of whether deployment of the occupant protection device is desired, electrically coupling the occupant protection device and the crash sensor by means of an electrical bus, and directing the coded signal from the crash sensor over the bus to the occupant protection device to enable deployment of the occupant protection device. The coded signal may be generated by a crash sensor in response to a crash of the vehicle for which deployment of the occupant protection device might be required.
In order to achieve some of the objects set forth above and others, in one embodiment of a vehicle electrical wiring system in accordance with the invention, substantially all of the devices, and especially substantially all of the safety devices, are connected together with a single communication bus and a single power bus. In the preferred case, a single wire pair will serve as both the power and communication buses. When completely implemented each device on the vehicle will be coupled to the power and communication buses so that they will now have an intelligent connection and respond only to data that is intended for that device, that is, only that data with the proper device address.
The benefits to be derived from the vehicle electrical system described herein include at least at 50% cost saving when fully implemented compared with current wire harnesses. A weight savings of at least 50% is also expected. Most importantly, a multi-fold improvement in reliability will result. The assembly of the system into the vehicle is greatly simplified as is the repair of the system in the event that there is a failure in the wiring harness. Most of the connectors are eliminated and the remaining ones are considerably more reliable. Diagnostics on all devices on key-on can now be accomplished over the network with a single connection from the diagnostic circuit.
In contrast to other multiplexing systems based on zone modules, the communication to and from each device in the instant invention is bi-directional.
It is now believed that for side impacts, the airbag crash sensor should be placed in the door. There is reluctance to do so by the automobile manufacturers since in a crash into the A-pillar of the vehicle, for example, the wires leading to and form the door may be severed before the crash sensor activates. By using the two wire network as described herein, only two, or possibly four if a separate pair is used for power, of wires will pass from the door into the A-pillar instead of the typically fifty or more wires. In this case, the wires can be protected so that they are stronger than the vehicle metal and therefore will not sever during the early stages of the accident and thus the door mounted sensor can now communicate with the airbag in the seat, for example.
In the preferred system then, the power line or distribution network in the vehicle is used to simultaneously carry both power and data to all switches, sensors, lights, motors, actuators and all other electrical and electronic devices (hereinafter called devices) within the vehicle and especially all devices related to deployable restraints. Naturally, the same system will also work for vehicles having different voltages such as 48 volts. Also a subset of all vehicle devices can be on a net. Initially, for example, an automotive manufacturer may elect to use the system of this invention for the automobile safety system and later expand it to include other devices. The data, in digital form, is carried on a carrier frequency, or as pulse data as in the Ethernet protocol, and is separated at each device using either a microprocessor, xe2x80x9chigh-side driverxe2x80x9d or other similar electronic circuit. Each device will have a unique, individualized address and be capable of responding to a message sent with its address. A standard protocol will be implemented such as SAE J1850 where applicable. The return can be through vehicle ground comprising the vehicle sheet metal and chassis or through a wire.
The advantages of such a system when fully implemented are numerous, among which the following should be mentioned:
1. The amount of wire in the vehicle will be substantially reduced. There is currently about 500 or more meters of wire in a vehicle.
2. The number and complexity of connectors will be substantially reduced. There are currently typically about 1000 pin connections in a vehicle. When disconnection is not required, a sealed permanent connector will be used to join wires in, for example, a T connection. On the other hand, when disconnection is required, a single or dual conductor connector is all that is required and the same connector can be used throughout the vehicle. Thus, there will be only one or two universal connector designs on the vehicle.
3. The number of electronic modules will be substantially reduced and maybe even be completely eliminated. Since each device will have its own microprocessor, zone modules, for example, will be unnecessary.
4. Installation in the vehicle will be substantially easier since a single conductor, with branches where required, will replace the multi-conductor wire harnesses currently used. Wire xe2x80x9cchoke pointsxe2x80x9d will be eliminated.
5. Reliability will be increased based on system simplicity.
6. Two way or bi-directional communication is enabled between all devices. This simplifies OBD2 (On Board Diagnostic Level 2 now required by the US Government for pollution control) installation, for example.
7. All devices on the vehicle are diagnosed on key-on. The driver is made aware of all burned out lamps, for example before he or she starts the vehicle.
8. Devices can be located at optimum places. A side impact sensor can be placed within the vehicle door and still communicate with an airbag module located in the seat, for example, with high reliability and without installation of separate wiring. In fact, only a single or dual wire is required to connect all of the switches, sensors, actuators and other devices in the vehicle door with the remainder of the vehicle electrical system.
9. Electro-magnetic interference (EMI) Problems are eliminated. The driver airbag system, for example would have the final circuit that deploys the airbag located inside the airbag module and activated when the proper addressed signal is received. Such a circuit would have an address recognition as well as diagnostic capabilities and might be known as a xe2x80x9csmart inflatorxe2x80x9d. EMI, which can now cause an inadvertent airbag deployment, ceases to be a problem.
10. Vehicle repair is simplified and made more reliable.
It is important that any wire used in this embodiment of the invention be designed so that it won""t break even in an accident since if the single bus breaks the results can be catastrophic. Additionally, the main bus wire or pair of wires can be in the form of a loop around the vehicle with each device receiving its messages from either direction such that a single major break can be tolerated. Alternately, a tree or other convenient structure can be used and configured so that at most a single branch of the network is disabled.
It should be understood that with all devices having access to the network, there is an issue of what happens if many devices are attempting to transmit data and a critical event occurs, such as a crash of the vehicle, where time is critical, i.e., will the deployment of an airbag be delayed by this process. However, it is emphasized that although the precise protocol has not yet been determined pending consultation with a customer, protocols do exist which solve this problem. For example, a token ring or token slot network where certain critical functions are given the token more frequently than non-critical functions and where the critical device can retain the token when a critical event is in progress is one solution. A crash sensor, for example, knows that a crash is in progress before it determines that the crash severity requires airbag deployment. That information can then be used to allocate the bandwidth to the crash sensor. An alternate approach is to use a spread spectrum system whereby each device sends and is responsive to a pattern of data that is sorted out using correlation techniques permitting any device to send and receive at anytime regardless of the activity of any other device on the network.
Another issue of concern is the impact of vehicle noise on the network. In this regard, since every device will be capable of bi-directional communication, standard error checking and correction algorithms are employed. Each device is designed to acknowledge receipt of a communication or the communication will be sent again until such time as receipt thereof by the device is acknowledged. Calculations show that the bandwidth available on a single or dual conductor is much greater than required to carry all of the foreseeable communication required within an automobile. Thus, many communication failures can be tolerated.